The increasing density of electrical connections in semiconductor devices has pushed conventional packages to their design limit. Heat generated by the semiconductor devices needs to be dissipated immediately to prevent them from overheating. As the semiconductor devices become denser, the generated heat also increases correspondingly. More and more packages are now designed with heat sinks or heat slugs to enhance the ability to dissipate heat.
With smaller package footprint, ball grid array (BGA) packages have been introduced and developed several years ago. BGA includes a family of package ‘styles’, differentiated primarily by construction materials and techniques, such as plastic (PBGA) or ceramic (CBGA). Other BGA packages include tape automated bonding ball grid array (TAB-BGA) and cavity down (CD-BGA) type of construction.
Higher device working frequency (3.3 MHz and above) with increased clock speed rates have required the creation of other versions of BGA: enhanced BGA (EBGA), thermally enhanced BGA (TEBGA I & II), heat spreader BGA (HS-BGA), and micro super BGA (mBGA or m Super-BGA). However, all BGA packages, regardless of package style, utilize solder attachments (balls) located directly underneath the package body. Thus, during reflow, a significant portion of the heat energy required to melt these connections must be conducted through the package body itself. Consequently, the materials and their relative locations within the package can influence the thermal profile of the package.
A BGA package typically includes a substrate, such as printed circuit board, made from reinforced polymer laminate material, i.e. bismaleimide triazine (BT) or a polyimide resin with series of metal traces on the top side. The metal traces are connected by vias to the bottom side of the substrate, and redistributed in an array grid around the periphery of the substrate. The semiconductor chip, having a plurality of bond pads, is mounted to the substrate using soft solder or epoxy. The bond pads are wires bonded to connect the chip to the package substrate or are bonded using solder bump for flip-chips. The whole package is then encapsulated with a molding compound above the top portion of the package substrate. Lastly, the solder balls are attached and reflowed to enhance electrical conductivity.
However, a need still remains for a low-cost effective design with enhanced heat dissipation capability. In view of cost considerations and the increasingly limited space, it is increasingly critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.